An ophthalmologist or optician measures the eye and determines visual acuity. The demonstration of different variants in words is difficult and depends greatly on the explanation ability of the optician, the comprehension of the spectacle lens customer, and the given time. Without actually implementing spectacles of the recommended type, however, they cannot actually be demonstrated. Sometimes progressive spectacle lenses are classified as “incompatible” by the user. However, upon being measured again, these lenses prove to conform to the spectacle lens prescription and the user is satisfied only after choosing a different design. Thus, there is a need for objectification in the consultation and dispensing process for spectacles.
JP 3 893 760 A1 discloses the simulation of the visual impression of a wearer of spectacles or the generation of a virtual visual impression of a wearer of spectacles. For this purpose, an image on the retina of the wearer of spectacles is simulated on the basis of an original image and displayed. In particular, the movement of the image when gazing through a progressive lens taking account of head movements is also simulated.
EP 2 341 388 A1 describes a development of the simulation described in JP 3 893 760 A1 which takes account of the viewing direction of the wearer of spectacles and thus the change in the intersection point of the visual line—assigned to the viewing direction—from the eye through the progressive lens with respect to the original image. The simulation and display are carried out separately for each eye of the wearer of spectacles.
EP 2 856 931 A1 reveals a further development of the simulations described in the documents JP 3 893 760 A1 and EP 2 341 388 A1. Instead of an original image recorded beforehand, cameras assigned to the respective eyes and distance sensors aligned in the optical axial direction of the cameras are provided. The viewing direction of the wearer of spectacles controls the alignment of the cameras and distance sensors. The images recorded by the cameras are used together with the distances of the object recorded by the cameras, the distances being determined by the distance sensors, instead of the abovementioned original image as input variables for the simulation. The display is carried out on a so-called head-mounted display that is incorporated into the same carrier for the cameras and the distance sensors.
WO 2007/056795 A1 discloses an arrangement similar to that described in EP 2 856 931 A1. In particular, a head-mounted spectacle lens simulator is described therein. The head-mounted spectacle lens simulator comprises—depending on the embodiment as a mono or stereo image simulator—one or two cameras that record the scenery of the wearer before or during the simulation. The simulation can take account of the imaging aberrations of the subject's eye that are measured by a wavefront sensor. Furthermore or alternatively, the simulation can take account of the head and/or eye movements recorded by corresponding head and/or eye movement detectors, so-called head and/or eye trackers. The simulation can furthermore include the spectacle lens design, i.e., the optical properties of the spectacle lens for the observer depending on the respective viewing point through the computationally represented spectacle lens. Single-vision lenses, bifocal lenses or progressive lenses may be involved. The simulation can also include the frame size of the respective spectacle lenses. Finally, besides the visual impression on the basis of head movements and different viewing directions through the respective spectacle lens, it is also possible to superimpose areas or lines on the scenery represented for the observer in order to illustrate for the observer zone boundaries, such as e.g., near and distance regions and progression channel in the case of a progressive lens.
DE 10 2009 008 876 A1 describes a visual impression simulation unit for simulating and displaying the person's actual visual impression on the basis of measured refraction errors of an eye of a person and prescription values determined therefrom. The visual impression simulation unit may operate e.g., according to one of the methods described in the MSc thesis by Woojin Matthew Vu “Simulation of Vision through an Actual Human Optical System,” in 2001 at the University of California, Berkley, USA or WO 2004/112576 A2. Both documents describe methods as to how the visual impression can be simulated on the basis of wavefront data. In this regard, e.g., the prescription values determined in the preceding step are subtracted from the measured wavefront and the visual impression is simulated by convolving the residual wavefront with a suitable test image.
WO 01/88654 A2 reveals a computer configured to display on a screen the visual impression of a wearer of spectacles when gazing through a plurality of different spectacle lenses. In particular, the document reveals the representation of a scene which the wearer of spectacles would perceive when gazing through photochromic spectacle lenses under different weather conditions. Furthermore, a description is given of gazing through tinted spectacle lenses, bifocal and progressive spectacle lenses, scratch-resistant spectacle lenses, and antireflection-coated spectacle lenses.
During the technical trade fair for spectacles Silmo 2015, the presentation of a head-mounted display (HMD) was announced, which purportedly is able to display three-dimensionally the visual impression through different spectacle lenses for the wearer of spectacles. The presentation can be found at www.acuite.fr/actualite/produit/76619/un-casque-3d-en-magasin-pour-mieux-demontrer-les-benefices-des-verres-signe?utm_campaign=ecAcuite&utm_medium=flashoptic&utm_source=flashoptic (last accessed Jul. 9, 2015). However, the functioning of this device is not described therein.
DE 10 2014 107 938 A1, reveals a display device in the form of an HMD comprising a holding device which can be placed onto the head of a user, and comprising a first imaging optical unit secured to the holding device and designed to image an image generated in an image plane as a virtual image such that the user can perceive the image with a first eye when the holding device is in the state placed on the head.
The display device may have a second imaging optical unit for the observer's second eye, which is preferably structurally identical to the first imaging optical unit. In this case, this is also referred to as a stereo image observer.
The first imaging optical unit of the display device according to DE 10 2014 107 938 A1 has a first lens having negative refractive power and a second lens having positive refractive power, the second lens being spaced apart from the first lens. The first lens is positioned nearer to the image plane than the second lens. An image generator is arranged in the image plane and generates the image that is imaged by means of the first imaging optical unit. The image generator is arranged in an exchangeable fashion in the image plane.
DE 10 2014 017 534 A1 describes a display device similar to the display device as described in DE 10 2014 107 938 A1. This display device comprises a holding device which can be placed onto the head of a user, and a first imaging optical unit secured to the holding device and designed to image an image generated in an image plane as a virtual image such that the user with the holding device placed onto the head can perceive the image with a first eye. In a departure from the embodiment according to DE 10 2014 107 938 A1, the first imaging optical unit has as imaging element exactly one first lens having a first and a second interface. The two interfaces are curved aspherically in each case. As in the embodiment described previously, an image generator is arranged in the image plane and generates the image that is imaged by means of the first imaging optical unit. The image generator in that case is arranged in an exchangeable fashion in the image plane.
With regard to subjective refraction determination, according to de.wikipedia.org/wiki/Refraktion#Bestimmung_der_subjektiven_Refraktion (last accessed on Jul. 9, 2015) it is known in the art to position in front of the person to be examined successively systematically different lenses, so-called measuring spectacle lenses, and to ask about an improvement or deterioration in the visual impression. In this case, such visual symbols which are also used for determining visual acuity are generally offered as objects for observation. The process of selecting the measuring spectacle lenses and positioning them in front of a person is greatly accelerated by the use of a phoropter, an apparatus that can be used to switch back and forth rapidly between different measuring spectacle lenses. It is also possible to use “measuring spectacles” for this procedure. Determination is continued until no further improvement of visual acuity is obtained by varying the correction values offered. The optical power of the measuring spectacle lenses thus selected, taking account of the examination distance, is then the subjective refraction.
EP 2 363 058 B1 discloses a subjective refraction determining device comprising two lenses. The first lens comprises a plurality of adjacent first zones arranged over the lens in a first direction, wherein each first zone has a different average power. A plurality of adjacent second zones are arranged over the first lens in a second direction perpendicular to the first direction, wherein each second zone has a different cylinder power. The first zones arranged over the first lens in the first direction overlap the second zones arranged over the first lens in the second direction. Both the average power and the cylinder power vary across the first lens by four diopters or more. The second lens has a constant average power arranged relative to the lens such that an observer can observe a target through the second lens and the lens having the varying average power and the varying cylinder power.
Although the above-described devices in which the visual impression of a wearer of spectacles is displayed by simulation have fundamentally proved worthwhile for demonstrating optical properties of spectacle lenses, there is a need for a simple demonstration device.